media: Add UMA to report CDM interface version being used

media/cdm/cdm_wrapper.h

Index: media/cdm/cdm_wrapper.h
diff --git a/media/cdm/cdm_wrapper.h b/media/cdm/cdm_wrapper.h
index 20cdaad61344ec7e8ac8d9fb372eb6048571ef6b..75a1fe0b090546e412b827d758bdf75f02781dce 100644
--- a/media/cdm/cdm_wrapper.h
+++ b/media/cdm/cdm_wrapper.h
@@ -58,7 +58,10 @@ class CdmWrapper {
                             GetCdmHostFunc get_cdm_host_func,
                             void* user_data);
 
-  virtual ~CdmWrapper(){};
+  virtual ~CdmWrapper() {}
+
+  // Returns the version of the CDM interface that the created CDM uses.
+  virtual int GetInterfaceVersion() = 0;
 
   virtual void Initialize(bool allow_distinctive_identifier,
                           bool allow_persistent_state) = 0;
@@ -137,6 +140,8 @@ class CdmWrapperImpl : public CdmWrapper {
 
   ~CdmWrapperImpl() override { cdm_->Destroy(); }
 
+  int GetInterfaceVersion() override { return CdmInterface::kVersion; }
+
   void Initialize(bool allow_distinctive_identifier,
                   bool allow_persistent_state) override {
     cdm_->Initialize(allow_distinctive_identifier, allow_persistent_state);